The present invention is therefore based on the objective of providing a guiding device of the type mentioned at the outset as well as a sawing machine comprising such a guiding device, by which oscillations in the saw band or the sawblade can be damped more effectively.
This objective is attained in a guiding device as well as a sawing machine having one or more of the features of the invention.
Preferred embodiments and further developments of the guiding device according to the invention as well as the sawing machine according to the invention are provided below and in the claims.
According to the invention it is therefore provided that at least one gliding part and/or at least one roll are provided at the holder in a fashion movable in reference to the holder, namely preferably essentially perpendicular in reference to a direction of travel of the saw band or the sawblade, i.e. thus essentially in a manner movable towards the saw band or the sawblade and away therefrom. This movement is triggered according to the invention by at last one Piezo-actuator.
Piezo-actuators include piezo-electric materials, such as quartz or barium titanate, for example, and utilize the piezo-electric effect by which a deformation of the crystalline structure of the piezo-electric material occurs by an electric voltage being applied. This way, piezo-actuators can generate strong mechanic forces and here deform in a very short period such that by an appropriate modulation of the applied voltage oscillations are generated with frequencies in the kHz-range.
This feature of the piezo-actuators used according to the invention allows to actively damp oscillations in the saw band or the sawblade, which compromise the sawing result. Here it is preferred that a control unit for controlling and/or regulating the motions of at least one piezo-actuator is a part of the guiding device according to the invention, which comprises for example a set of different control programs for controlling at least one piezo-actuator. Based on saw parameters to be entered in the control unit, such as the profile and material of the workpiece to be sawed, or the form and the material as well as the speed of motion of the saw band or the sawblade or also the speed of the sawing feed a control program is selected that generates motions, particularly counter-oscillating motions of the piezo-actuator, in order to counteract and/or to damp vibrating motions of the saw band or the sawblade typically developing when sawing with respective sawing parameters.
The optimized, active damping of vibrations can be achieved within the scope of a preferred embodiment of the guiding device according to the invention by evaluating signals from a sensor, which detects oscillating motions of the saw band or the sawblade. With the help of an appropriate algorithm the control unit can calculate from the detected oscillating motions of the saw band and/or the sawblade counter-oscillating motions and generate them with the piezo-actuator according to the invention, ensuring an optimized active damping of oscillations.
Such a sensor for detecting oscillating motions of the saw band or sawblade can be a solid borne sound sensor or an optical vibration sensor; however, at least one or an additional piezo-actuator may be used as a sensor for detecting oscillating motions, because the piezo-electric effect works in both directions: Any deformation of the piezo-electric materials leads to a change of the voltage applied and vice versa.
The control unit of the guiding device, which based on sensor signals generates counter oscillation motions of at least one piezo-actuator in order to optimize an active oscillation damping, can also be equipped with a self-learning algorithm which uses the sensor signals as a control of success and adjusts the counter-oscillating motions respectively in a self-learning fashion.
If several piezo-actuators are provided in the holder of the guiding device according to the invention (which will usually be the case) it may be advantageous to embody the control unit such that it controls the different piezo-actuators in various fashions. Depending on the oscillation behavior of the saw band or the sawblade this may serve for optimizing the active damping of vibrations.
At least one piezo-actuator provided according to the invention is preferably arranged directly or indirectly between the gliding part and/or the roll and the holder. Here it may be advantageous to allow the piezo-actuator to act via a lever arrangement upon the gliding part and/or the roll. By a lever arrangement the deformation and/or the adjustment path of the piezo-actuator can be transmitted and thus increased and the piezo-actuator can be arranged at a certain distance from the saw band or the sawblade, which can simplify its electric contacting.
For the lateral guidance of the saw band or sawblade usually gliding parts are provided, which can be moved via the piezo-actuator actively towards the saw band and/or the sawblade and away therefrom. For the protection of the piezo-actuator it is here preferred for the gliding parts to be arranged on pressure plates, which can be moved in reference to the holder. The piezo-actuators can then be arranged between the pressure plates and the holder, in order to move the pressure plate, while simultaneously they are shielded by the pressure plate from the saw band and/or the sawblade.
For the guidance of the back of the saw band in a band saw machine it is preferred to use a roll, which is held in bearings, which are directly or indirectly movable via at least one piezo-actuator in reference to the holder. Such bearings may for example be arranged in a forked bearing bridge, which is connected via piezo-actuators to the holder, with the bearing bridge in turn shielding the piezo-actuators from the saw band.
In addition to the mobility of the gliding parts and/or rolls of a guiding device according to the invention via piezo-actuators according to the invention, within the scope of the present invention here a hydraulic mobility of the gliding parts and/or rolls may be provided as well.